How human runners regulate footsteps on uneven terrain

Abstract

AbstractRunning was crucial for human evolution, especially for persistence hunting. But how people remain stable on uneven natural terrain is not understood. In particular, we do not know how runners manage competing demands on their attention, like seeking level ground areas to step on versus seeking out prey. Previous work used step-like terrain with height variations but not the more destabilizing combination of height and slope variations like a natural undulating terrain. So we studied human runners on undulating uneven terrain and measured their energetics, kinematics, and ground forces. Here we show that runners do not selectively land their feet on more level areas. Instead, they remain stable using their body’s mechanical response and possibly occasional feedback corrections, with little increase in energy consumption relative to flat ground. These findings may explain how persistence hunters can devote visual attention to tasks other than stability while running on uneven ground.